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Re: Macro for(UP_and_DOWN) and 3 similar. (issue 2491) (issue 6109046)

From: James
Subject: Re: Macro for(UP_and_DOWN) and 3 similar. (issue 2491) (issue 6109046)
Date: Fri, 27 Apr 2012 17:58:19 +0100


On 27 April 2012 15:56, Phil Holmes <address@hidden> wrote:

> It may depend on your hardware whether this makes sense.  My Ubuntu build
> box can multithread within the VM, whereas my (older) Windows box can't.

Depends on the paravirtualization.


Most modern server hardware has 'vt-enabled' CPUs on them (even more
recent consumer laptop/desktop hardware). This makes a world of
difference to speed and performance.

You then need to tick a box more or two to enable that stuff in VBox
or KVM. Remember though that LilyDev is 32bit so if you use KVM you
must not go over 4096 for your RAM (even if you have more) else, I
found, it will just default to 128mb! Vbox is a bit more smart, but
you still cannot address more than 4GB of RAM in a 64bit VBox install
using LilyDev.

So if you have lots of GBs of RAM to play with, from my experience,
KVM is much more 'forgiving' in terms of having multiple VMs using
more CPUs than you have in reality. Vbox isn't. I haven't used it for
a while now but it will stop you allocating more CPUs that you have
physically on multiple machines even if in reality one or more VMs are
not doing much. KVM will spread the load (so to speak) better and I
often forget and run 3 VMs using theoretically using 21 Virtual CPUs!
I only notice when I do a make -j7 and am working on one of the other does kind of grind to a halt at that point. :)


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